1. Field of the Invention
The present invention generally relates to photoresist stripper compositions used in the manufacture of semiconductor devices, and more particularly, the present invention relates to photoresist stripper compositions which are especially suitable for use in the edge bead removal (EBR) and rework processes of photolithography.
2. Description of the Related Art
Rework and edge bead removal (EBR) processes are common processes encountered during photolithography of semiconductor wafers or substrates.
The rework process is carried out when a photoresist that has been coated onto a wafer contains defects. In this case, the defective photoresist is completely removed from the wafer using a stripper composition, thereby allowing the wafer to be reused.
On the other hand, EBR results from certain characteristics of the photoresist coating process. That is, the photoresist is coated onto a wafer by dispensing the photoresist material onto a surface of the wafer while the wafer is rotating. As a result, the photoresist material tends to accumulate at the edge of the wafer, forming a so-called edge bead. Also, during the spraying process, photoresist material inevitably becomes coated onto the backside of the wafer. Accordingly, in the EBR process, a stripper composition is used to remove any unwanted photoresist from the edge and backside of the wafer.
During both the rework and EBR process, it is important that the photoresist not dissolve too slowly or incompletely in the stripper composition, otherwise residual contaminants (photoresist) may remain on the substrate after the stripping process. Any such contaminants can reduce device yield and adversely impact product reliability.
In the meantime, to accommodate for increased degrees of integration of semiconductor devices, new photoresist are being developed. For example, a photoresist having novolak resin as a main component has been developed for application with light of I-line or G-line wavelengths. Also, amplified type photoresists which respond to an excimer laser or deep ultraviolet (DUV) also have been employed.
It is therefore desirable that a stripper composition for stripping the photoresist exhibit good solubility with respect to the various types of photoresists now being utilized. However, the solubility of conventional photoresist stripper compositions is often insufficient, particularly when used to remove DUV photoresists.
Further, a primary drawback to present photoresist stripper compositions is that they are expensive. For example, one commonly used stripper composition includes ethyl lactate(EL), ethyl-3-ethoxy propionate(EEP) and gamma-butyro lactone(GBL) (U.S. Pat. No. 5,866,305). Unfortunately, however, the main component is EEP(75 wt %), which is quite expensive. Also, DUV photoresists in particular dissolve too slowly using this composition.
Accordingly, there is a demand for photoresist stripper compositions which exhibit favorable stripping characteristics in both the rework and EBR processes, and with respect to different types of photoresists, yet which can be manufactured at relatively low cost.
According to one aspect of the present invention, a photoresist stripper composition consist essentially of a mixture of an acetic acid ester, xcex3-butyrolactone (GBL), and a non-acetate ester. The acetic acid ester may be one or more of n-butyl acetate (NBA), amyl acetate, ethyl aceto-acetate, and isopropyl acetate, with NBA being preferable. The non-acetate ester may be one or more of ethyl lactate (EL), ethyl-3-ethoxy propionate (EEP) and methyl-3-methoxy (MMP).
The mixture may include 8-95 wt % of the acetic acid ester, 0.1-13 wt % of the GBL, and 3-80 wt % of the non-acetate type ester. More preferably, the mixture may include 50-90 wt % of the acetic acid ester, 0.1-7 wt % of the GBL, and 10-70 wt % of the non-acetate type ester.
In the case where the acidic acid ester is NBA and the non-acetate type ester is EL, the mixture may include 50-85 wt % of the NBA, 1-13 wt % of the GBL, and 10-40 wt % of the EL. More preferably, the mixture may include 55-85 wt % of the NBA, 1-7 wt % of the GBL, and 10-40 wt % of the EL.
In the case where the acidic acid ester is NBA and the non-acetate type ester is EEP, the mixture may include 20-90 wt % of the NBA, 0.1-13 wt % of the GBL, and 10-70 wt % of the EEP. Preferably, the mixture may include 30-89 wt % of the NBA, 0.1-7 wt % of the GBL, and 20-70 wt % of the EEP. More preferably, the mixture may include 30-89 wt % of the NBA, 0.5-5 wt % of the GBL, and 10-65 wt % of the EEP.
In the case where the acidic acid ester is NBA and the non-acetate type ester is MMP, the mixture may include 50-90 wt % of the NBA, 1-13 wt % of the GBL, and 5-40 wt % of the MMP. More preferably, the mixture may include 55-90 wt % of the NBA, 1-7 wt % of the GBL, and 5-40 wt % of the MMP.
According to another aspect of the present invention, a photoresist stripper composition consist essentially of a mixture of an acetic acid ester, xcex3-butyrolactone (GBL), and an alcohol derivative. The acetic acid ester may be one or more of n-butyl acetate (NBA), amyl acetate, ethyl aceto-acetate, and isopropyl acetate, with NBA being preferable. The alcohol derivative may be one or more of propylene glycol monomethyl ester (PGME) and propylene glycol monomethyl ester acetate (PGMEA).
The mixture may include 42-90 wt % of the acetic acid ester, 1-13 wt % of the GBL, and 5-45 wt % of the alcohol derivative. More preferably, the mixture may include 50-85 wt % of the acetic acid ester, 1-7 wt % of the GBL, and 10-40 wt % of the alcohol derivative.
In the case where the acetic acid ester is NBA and the poly alkyl alcohol derivative is PGME, the mixture may include 50-85 wt % of the NBA, 1-13 wt % of the GBL, and 5-40 wt % of the PGME. More preferably, the mixture may include 55-85 wt % of the NBA, 1-7 wt % of the GBL, and 10-30 wt % of the PGME.
In the case where the acetic acid.ester is NBA and the poly alkyl alcohol derivative is PGMEA, the mixture may include 50-85 wt % of the NBA, 1-13 wt % of the GBL, and 10-40 wt % of the PGMEA. More preferably, the mixture may include 55-85 wt % of the NBA, 1-7 wt % of the GBL, and 10-40 wt % of the PGMEA.
Further, other non-major components such as surfactants may be added to the afore-described stripper compositions of the present invention. In the case of surfactants, it is preferable that the surfactant constitute less than 1 wt % of the mixture.